Presently there is a great need for an efficient method to euthanize spent laying hens with an emphasis on concern for the animal's welfare. Historically, spent laying hens had been processed for human consumption, however, there has been a great decline in this practice for the following reasons:
1. Consolidation of poultry meat processing plants has led to their sparse disbursement across America. Therefore, many egg farms are simply too far away to transport the birds, making it cost prohibitive.
2. Transportation of these old hens is complicated by the hens tendency to have brittle bones. This has led to problems with animal welfare issues, and problems with bone shards ending up in the chicken soup. Therefore, on-farm euthanasia for delivery to a rendering plant or composting has become much more a necessity.
Disease control has led to the need for rapid on-farm euthanasia because the birds should not be transported live if farmers are trying to contain an outbreak. Avian influenza (bird flu), salmonella, and other contagious diseases have become a much larger concern lately and have led to mass depopulations to control disease when necessary.
Animal welfare concerns have become a much larger issue over the years. Ag industry organizations attempt to self-regulate and make recommendations via producer groups and encourage producers to follow American Veterinary Medicine Association guidelines in order to reduce the incidences of bad publicity. Additionally, states are passing animal cruelty laws that are vague at best. Thus farmers are caught in the cross hairs. They may have the USDA or CDC forcing them to depopulate their flock on-farm, but lack the tools to do so and satisfy AVMA guidelines.
The present devices and methods for on-farm poultry euthanasia have been developed by individual farmers for their own needs and they would really rather not publicize that part of their business. One such method is Modified Atmospheric Killing (MAK) carts, but it is slow, inconsistent, and archaic and labor intensive. These involve some kind of manually filled cart, which is covered and filled with CO2 gas. There is no way to accurately measure the CO2 concentration, and it is all guesswork. Use of gas CO2 is employed, so using numbers provided by egg farmers using this method, you would need 34 bottles of CO2 gas to depopulate a 40,000 bird coop versus 2-3 bottles of liquid CO2 with operation of the disclosed technology. A person has to load the cart, then begin the process and wait until death. The animals are gassed in the barn, or taken out. Either way, the doors to the barn are open and the increased light makes the animals more nervous and difficult to catch. Moreover, many carts are needed. The cart is then pushed out and unloaded, and from there the dead birds have to be moved into a truck for transport
Another method is the use of covered dump trucks. A tarp is placed over the bed of a dump truck, leaving a hole large enough to toss the live birds in. Once the floor of the dump truck is covered with birds they close the hole and then inject CO2 into the bed of the truck. This is very hard on the birds as they are tossed about and these old hens have brittle bones which break easily. Lots of CO2 is wasted because the whole volume of the truck is gassed, then the door is opened for the next batch allowing the CO2 to escape, so it is not efficient.